<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>BFC演示</title>
</head>
<style>
    .box1{
    width: 200px;
    height: 200px;
    background-color: #bfa;
   /* float: left; */
   overflow: hidden;
    }
    .box2{
    width: 200px;
    height: 200px;
    background-color: orange;
    }
    .box3{
    width: 100px;
    height: 100px;
    background-color: orange;
    margin-top: 100px;
    }
</style>
<body>
    <div class="box1">
        <div class="box3">

        </div>
    </div>
    <!-- <div class="box2">

    </div> -->
 
</body>
</html>